Background
Benign tumors of the small bowel are rare clinical entities that often remain asymptomatic throughout life. [1, 2, 3, 4] Despite comprising 75% of the length and 90% of the surface area of the gastrointestinal (GI) tract, the small bowel harbors relatively few primary neoplasms and fewer than 2% of GI malignancies. [5]
Benign small-bowel tumors may develop as a single lesion or as multiple lesions of several subtypes. Subtypes include hyperplastic polyps, adenomas, gut stromal tumors, lipomas, hemangiomas, and those associated with Peutz-Jeghers syndrome. [6]
These tumors are generally characterized by slow growth and delayed clinical presentation. They often remain inherently asymptomatic, only to be discovered incidentally at autopsy.
Strict medical management currently has no role in benign small bowel tumors. Surgical excision of small bowel tumors remains the recommended therapy. (See Treatment.)
Pathophysiology
Benign small-bowel tumors may be found throughout the duodenum, jejunum, and ileum (in order of increasing frequency). Tumors may be single, multiple, or widespread, that is, as part of a polyposis syndrome. Three growth patterns have been identified, as follows:
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Intraluminal
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Infiltrative
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Serosal
Intraluminal lesions are most often associated with the development of secondary bowel obstruction and intussusception, whereas serosal lesions are linked to small-bowel volvulus.
Several factors have been suggested to explain both the scarcity of small-bowel lesions and the infrequency of their malignant transformation. [7] First, rapid intestinal transit through the small bowel limits contact time to the small bowel mucosa. Second, greater fluidity of small-bowel chyme may dilute luminal irritants. Third, alkaline pH may play a role, as may the low bacterial colony counts of the small bowel. Finally, higher levels of benzyl peroxidase (thought to detoxify potential carcinogens) have been detected in the small bowel.
Together, with increased levels of immunoglobulin A and widespread gut lymphoid tissue, these factors may impede the growth and development of tumors and their malignant transformation.
Epidemiology
Benign small-bowel lesions have been documented in persons of all age groups, though the mean age of presentation reportedly is between the fifth and sixth decades of life. Several series have noted a slight predominance in males compared to females. No racial or ethnic predisposition has been discovered.
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Benign neoplasm of the small intestine. Arteriogram demonstrating small bowel gut stromal tumor, indicated by round tumor blush in lower right corner of the image.
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Benign neoplasm of the small intestine. Intraoperative view of an ependymal small bowel stromal tumor. Notice the narrow lesion stalk and high degree of vascularity.
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Benign neoplasm of the small intestine. Cross section of a gross ependymal small bowel stromal tumor after removal. Mixed stromal elements and a high degree of cellularity are apparent.
